1. capable, competent. Effective,effectual,efficacious,efficient refer to that which is able to produce a (desired) effect. Effective is applied to that which has the power to, or which actually does, produce an effect: an effective action, remedy, speech.Effectual is used especially of that which produces the effect desired or intended, or a decisive result: An effectual bombardment silenced the enemy.Efficacious suggests the capability of achieving a certain end: an efficacious plan, medicine.Efficient (applied also to persons) implies the skillful use of energy or industry to accomplish desired results with little waste of effort: efficient methods; an efficient manager.2. operative. 3. telling.

effective

(prenominal) actual rather than theoretical; real: the effective income after deductions

5.

(of a military force, etc) equipped and prepared for action

6.

(physics) (of an alternating quantity) having a value that is the square root of the mean of the squares of the magnitude measured at each instant over a defined period of time, usually one cycle See also root mean square

late 14c., from French effectif, from Latin effectivus "productive, effective," from effect-, stem of efficere (see effect (n.)). Effectively in the sense of "actually" is attested by 1650s. Related: Effectivity.